Protected areas are key conservation tools intended to increase biodiversity and reduce extinction risks of species and populations. However, the degree to which protected areas achieve their conservation goals is generally unknown for many protected areas worldwide. We assess the effect of protected areas on the abundance of 196 common, resident bird species. If protected areas were beneficial to avian biodiversity, we expect landscapes with a higher proportion of protected areas will have higher densities of species compared to landscapes with no protection.
Location
Greater Gauteng region, South Africa.
Methods
We analysed bird survey data collected over regular grid cells across the study area. We estimated bird abundance in relation to the proportion of a grid cell that was protected with the Royle–Nichols model and fitted the model once for each of the species. We examined variation in estimated abundance as a function of avian guild (defined by the type of food a species preferentially ate and its foraging mode) with a regression tree analysis.
Results
Abundance was significantly positively related to the proportion of protected areas in grid cells for 26% of the species, significantly negatively related in 15%, and not significantly related in 59% species. We found three distinct guild groups which differed in their average abundance, after accounting for associated variance. Group 1 consisted of guilds frugivores, ground‐feeders, hawkers, predators, and vegivores and average abundance was strongly positively related to the proportion of protected areas. Group 2 included granivores, and average abundance was strongly negatively related to proportion of protected areas. Group 3 included gleaners only, and average abundance was not related to proportion of protected areas.
Main conclusion
We conclude that the network of protected areas within the greater Gauteng region sustained relatively higher abundances of common birds and thus perform an important conservation role. 相似文献
Background: Understanding how factors related to environment and geographical distance explain community variation allows insights about how ecological niche and neutral processes control tropical community assembly.
Aims: Quantify how variation in regional tree community richness and composition in a humid tropical forest across a mountain chain are related to niche and putative neutral processes.
Methods: We used a variation partitioning routine based on Redundancy Analysis to model tropical tree community richness and composition within three distinct elevation belts, as a function of environment and spatial structure, using data from 32 studies in the Serra do Mar Range, south-eastern Brazil.
Results: Environmental effects were greater than spatial structure effects to explain community variation in the three elevation belts. There was a trend of decreasing spatial structure effects while environmental effects remained constant from lower to higher elevations. Patterns were congruent for species richness and composition.
Conclusions: We suggest that on tropical mountains, niche-related processes are equally relevant for tropical forest community assembly at all elevations, while neutral processes become weaker towards higher elevations. Determining if this trend is a consequence of the greater heterogeneity of environmental conditions associated with higher elevations in tropical mountainous terrain remains an important area of research. 相似文献
正随着全球气候变化的日趋加剧,动物对环境变化的反应模式和机制引起了越来越多研究者的兴趣(Canale and Henry,2010)。能量的获取与消耗是动物生存的关键,同时也是维持体重平衡的关键(Wang et al.,2003)。消化系统表型可塑性是动物个体的适应性特征,能帮助它们应对食物资源的变 相似文献
Understanding population change is essential for conservation of imperiled species, such as amphibians. Worldwide amphibian declines have provided an impetus for investigating their population dynamics, which can involve both extrinsic (density‐independent) and intrinsic (density‐dependent) drivers acting differentially across multiple life stages or age classes. In this study, we examined the population dynamics of the endangered Barton Springs Salamander (Eurycea sosorum) using data from a long‐term monitoring program. We were interested in understanding both the potential environmental drivers (density‐independent factors) and demographic factors (interactions among size classes, negative density dependence) to better inform conservation and management activities. We used data from three different monitoring regimes and multivariate autoregressive state‐space models to quantify environmental effects (seasonality, discharge, algae, and sediment cover), intraspecific interactions among three size classes, and intra‐class density dependence. Results from our primary data set revealed similar patterns among sites and size classes and were corroborated by our out‐of‐sample data. Cross‐correlation analysis showed juvenile abundance was most strongly correlated with a 9‐month lag in aquifer discharge, which we suspect is related to inputs of organic carbon into the aquifer. However, sedimentation limited juvenile abundance at the surface, emphasizing the importance of continued sediment management. Recruitment from juveniles to the sub‐adult size class was evident, but negative density‐dependent feedback ultimately regulated each size class. Negative density dependence may be an encouraging sign for the conservation of E. sosorum because populations that can reach carrying capacity are less likely to go extinct compared to unregulated populations far below their carrying capacity. However, periodic population declines coupled with apparent migration into the aquifer complicate assessments of species status. Although both density‐dependent and density‐independent drivers of population change are not always apparent in time series of animal populations, both have important implications for conservation and management of E. sosorum. 相似文献
Samples from sheltered nearshore waters in south-western Australia, in which Sillago schomburgkii spends its entire life cycle, have been used to determine the age structure, growth rate, age and length at first sexual maturity, and spawning period of this whiting species. Several S. schomburgkii reached four to seven years in age and one 12+ fish was caught. The respective maximum and asymptotic lengths (L) were 350 and 333 mm for females and 348 and 325 mm for males, while the growth coefficients (K) for females and males were 0.53 and 0.49, respectively. Sexual maturity was attained by both sexes of S. schomburgkii at ca. 200 mm, a length reached at the end of the second year of life. Monthly trends exhibited by gonadosomatic indices, the proportions of mature gonads and the prevalence of advanced oocytes and post-ovulatory follicles demonstrate that S. schomburgkii spawns predominantly from December to February. The presence of yolk vesicle and yolk granule oocytes and post-ovulatory follicles in the same ovaries during the spawning period, indicate that S. schomburgkii is a multiple spawner. The patterns of growth of the five Sillago species, that occur in south-western Australian marine waters, fall into two categories. The first, which consists of S. burrus and S. robusta, has a small L, i.e. < 190, and a high growth coefficient (K), i.e. 1.0, whereas the second, which comprises S. schomburgkii, S. vittata and S. bassensis, attain a larger size, i.e. L > 00 mm, and has a low K, i.e. 0.5. The lengths and ages at maturity of S. schomburgkii, S. bassensis, S. burrus and S. robusta, as well as of S. analis and S. flindersi found elsewhere in Australia, are linearly related to their asymptotic lengths and maximum ages, respectively. The two smallest species, S. burrus and S. robusta, attain maturity at ca. 130 mm. However, the former species, whose juveniles occupy productive nearshore waters, grows rapidly and reaches this length by the end of the first year of life, whereas the latter species, which is restricted to deeper waters, grows more slowly and thus does not attain this length until a year later. Sillagoflindersi, which is slightly larger than S. burrus and S. robusta, migrates out into deeper waters and attains maturity at ca. 170 mm and two years of age. Although S. schomburgkii, S. analis and S. bassensis attain maturity at ca. 200 mm and reach similar lengths, the first two of these species, which remain in nearshore waters and display more rapid growth, reach maturity one year earlier than the last species, which migrates out into deeper and presumably less productive waters. While S. vittata reaches a similar size and likewise migrates out into deep waters, it reaches maturity earlier, i.e. at the end of its first year of life. 相似文献